- update to 0.13.0:
* Single quote the callables name (when submission errors
* Updated from global requirements
* Reschedule failed periodic tasks after a short delay
* Fix wrong comparison in reject_when_reached
* Updated from global requirements
* Ensure all futures have completed before run returns
* Allow PeriodicWorker to skip executor shutdown in case of a preexisting executor
* Expose underlying futures.CancelledError
* Updated from global requirements
* Modification of the example code
* PeriodicWorker.create to accept arguments for periodic tasks
* Handle exceptions from executor.submit in PeriodicWorker
* Add periodics.is_periodic to check if object is a periodic task
* py26/py33 are no longer supported by Infra's CI

- Update to version 0.9.0
* Allow for providing different run work sync functions
* Have the executor stats object repr look like the watcher repr
* Add useful watcher '__repr__' function
* Some minor refactoring and comment/note addition
* No need for Oslo Incubator Sync
* Move most of green helper classes -> '_green.py'
* Add 'enabled' parameter to @periodic decorator
* Remove green worker reference to its executor
* Change ignore-errors to ignore_errors
* Activate pep8 check that _ is imported
* Handle the case where 0.199 is provided as runtime
* Just use a deque vs reverse pushing/popping
* Ensure new entry in immediates gets processed during wait(s)